Engine Management: Ignition Primary Circuits

Before starting the real Injection system, is important to understand what is key and important to know.
Let's start from the Aprilia Caponord ECU Injection system:


Therefore each injection coil is connected to +12V directly and grounded via the ECU circuit, the ECU Injector driver circuit looks like this:

The above picture represent a simple ECU circuit to drive the Fuel Injector. In essence, the ECU (the XE164 in the case of MaxPowerCMD) drives the first BJT transistor that acts as a voltage buffer to being able to drive the power MOS with higher voltages than the uC power supply (Aprilia RSV1000 Injector driver circuit is visible at Randomexploits).

Fuel Injectors
Let's copy some useful description of Fuel Injectors (or from Wiki).

The injector is an electromechanical device, which is fed by a 12 volt supply from either the fuel injection relay or the ECM. The injector is supplied with fuel from a common fuel rail. The injector pulse width depends on the input signals seen by the ECM from its various engine sensors, and varies to compensate for cold engine starting and warm-up periods, the initial wide pulse getting narrower as the engine warms to operating temperature. The pulse width also expands under acceleration and contracts under light load conditions. The injector has constant voltage supply while the engine is running and the earth path is switched via the ECM. An example of a typical voltage waveform is shown below in:

Note that the solenoid voltage increases up to about 60V after the power MOS is turned off (as a result of the constant elettro-magnetic field).

Is then easy to understand that every time that ECU drives a current trough the injector solenoid, after an initial set-up time, a fuel injection will occur, as visible in: fuel injection animation.

An electromechanical injector of course takes a short time to react, as it requires a level of magnetism to build before the pintle is lifted off its seat. This time is called the ‘solenoid reaction time’. This delay is important to monitor and can sometimes occupy a third of the total pulse width. A good example of the delay in opening can be seen in the example waveform shown below:

Note that the injector solenoid current is quite low, about 0.6A (Mr. Jefferies MyECU declares 1 - 2 A per injector)

The waveform is ‘split’ into two clearly defined areas. The first part of the waveform is responsible for the electromagnetic force lifting the pintle, in this example taking approximately 0.6 ms. At this point the current can be seen to level off before rising again as the pintle is held open. With this level off ind it can be seen that the amount of time that the injector is held open is not necessarily the same as the time measured. It is not however possible to calculate the time taken for the injector’s spring to fully close the injector and cut off the fuel flow.

Wiki documentation claims that

Injector pulsewidth typically ranges from 4 ms/engine-cycle at idle, to 35 ms per engine-cycle at wide-open throttle. The pulsewidth accuracy is approximately 0.01 ms.

The above voltage / current measurement scopes are showing a 4msec injection pulsewidth.

In my project MaxPowerCMD is not important to learn how to calculate the Fuel Injection pulsewidth since this is done by the motorbike ECU hardware. The motorbike ECU will feed the MaxPowerCMD with the desired Fuel Injection pulsewidth, but MaxPowerCMD will drive the Injector by changing the injection pulse, as for example:
- motorbike ECU pulsewidth = 5 msec
==> MaxPowerCMD [RPM, trottle, gear, ...] = 110%
==> MapowerCMD will drive a 5.5msec injection pulse
... and so on...

I think now is more clear what has to be done in software by using the powerful XE164 System on Chip.

MaxPowerCMD

Since my old Caponord need some "power injection" and that in any case the Traction Control need engine power adaptation, I thought is time to design my own Power Cmd.

The basic idea is to build up an electronic system to be connected at ECU inputs (trottle position, engine RPM, engine speed, ...) and outputs (injector driving signals, ...) so to change the injections maps during engine operation.

To clarify my initial ideas, I draw this:


So, let's try to explayin (and clarify myself also):
- on the left there is the original Motorbyke ECU, one Injector channel is drawn only. The Aprilia Caponord ECU drives the 4 Injectors exactly in such way: each Injector is connectd to +12V and the low side is switched by ECU (most likely using a power N-MOS), this is what I found from original Aprilia manual:


- between the fuel Injector (drawn on top right) a "fake injector" is inserted: this is needed to scope the Injector signal and to make sure that the ECU sense something and believes that Injector is still connected and working as expected:


- some logic gates must be inserted so to be able to replicate the original ECU signal as it is or to modify it:


- the last blocks is the MaxPowerCMD CPU itself, so the XE164:
.

How it works?
The basic idea is the following:
1- MaxPowerCMD has to sense the time when the motorbyke ECU would like to start an Injection sequence
2- MaxPowerCMD has to sense the Injector ON time at every revolution
==> with all information from 1 and 2, MaxPowerCMD would be able to reproduce the same Injection pulse as the motorbyke ECU would do
3- MaxPowerCMD has to measure the engine RPM
4- MaxPowerCMD has to measure the trottle position
==> with all information from 3 and 4, MaxPowerCMD would be able to access to a new Injection MAP as:

(rows: trottle position; columns: engine RPM speed)

==> the Injection MAP will have to be designed in % way, so 100% would indicate that the MaxPowerCMD will not change the motorbyke Injector pulse width. 50% would indicate a 50% shorter pulse and 150% an 1+1/2 pulse lenght. From this last requirement is now easy to understand why I have designed the logic gate block
to èermit to create an output signal that is shorter or longer then the ECU's imposed. The logic gate implementation also simplify the need to sincronize the MaxPowerCMD with the ECU signals since the MaxPowerCMD will simply impose the BYPASS mode just before any new injection sequence.
Before proceeding with the MaxPowerCMD I think is better to acquire more information about the Aprilia Caponord electronic injection system.

Injectors Test:
Aprilia indicated that a working Injector should have a resistence of about: 11,5 - 13 Ω at 20 °C (68 °F):

First Project (the simplest!) - Part 2

After a long time I restarted playing with servomotors to control the intake air system ram. Here my latest achievements with servo motors:

Stai tuned....

Weeling Display goes to PCB

It's time now to create a real PCB for the Weeling Display, so everyone of you could create his own Weeling Traction Control.

First of all, if you do not know, just have a look to the old posts:
Display It!
Display It! (Cont...)
Display It! (Cont...)
XE164 to Display connections

After the debug and the "in circuit" test, I drawn the schematic using Eagle (Eagle 5.5.0), here you can see it:

the above is the version with 9 displays in order to monitor:
- Gear (it's the display in the middle and it's a bigger model)
- Engine RPM or Speed
- Oil Temperature or Weeling Percentage (how much the rear weel is spinning in percentage)

Using the freeware Eagle version, is not possible to route a so big display, so I have reduced to 7 Displays and reoute as follows:


here the bottom Layer:


here the top Layer:


Component side is:


Component List:

Exported from WeelingDsiplay.sch at 5/2/2009 5:07:31 PM

EAGLE Version 5.5.0 Copyright (c) 1988-2009 CadSoft

Part Value Device Package Library Sheet

C1 100uF 25V
C2 100uF 10V
DIS1 HD-H103
DIS2 HD-H103
DIS3 HD-H103
DIS4 HD-H103
DIS5 HD-H103
DIS6 HD-H103
DIS7 HD-H103
DIS8 HD-H103
GEAR HD-N103 display-hp
IC1 4511N
IC2 7805
POWER 12V
R-D 330 ohm
R1 330 ohm
R2 330 ohm
R3 330 ohm
R4 330 ohm
R5 330 ohm
R6 330 ohm
R7 330 ohm
R8 330 ohm
R9 330 ohm
R17 330 ohm
R18 330 ohm
R19 330 ohm
R20 330 ohm
R21 330 ohm
R_A 330 ohm
R_B 330 ohm
R_C 330 ohm
R_E 330 ohm
R_F 330 ohm
R_G 330 ohm
T1 BC373-NPN-TO92
T2 BC373-NPN-TO92
T3 BC373-NPN-TO92
T4 BC373-NPN-TO92
T5 BC373-NPN-TO92
T6 BC373-NPN-TO92
T7 BC373-NPN-TO92
T8 BC373-NPN-TO92
T_GEAR BC373-NPN-TO92-CBE TO92-CBE transistor 1
X1 2520- 2520- PAK100/2500-20 con-3m 1

Currently I'm trying to build my first PCB, pictures will come soon...

Some pictures

Here the Weeling Box and display connected to the Yamaha R6:

Traction Control Connections

Weeling in mounted on my Yamaha R6, I still have to decide how to operate the Traction Control and how to connect it to the byke ECU.
Thinking and rethinking I had the idea to connect the traction control as the Electronic Shift units are doing. I found the following instructions:

so, if I have correctly understood the idea is to cut the power supply of the fuel injectors or of the spark coils.

Some friend told me that avoiding the spark firing could be that the spark get wet and therefore damaged... not really nice!!! Most likely is better to interrupt the fuel Injection.

From the R6 manual (2003 model), I have extracted the following electrical circuit:

(where "12" is the POWER SUPPLY RELAY and "18" are the fuel injectors).

The idea could be to use an HV P-MOS transistor and turn off the power supply of the fuel injectors as:


The driver circuit could look like:


Someone have some idea or suggestions?

Yamaha R6 (2003 Model) Water Temperature Sensor

Finally I was able to connect my "Welling" to the Yamaha R6 (2003 model) ECU in order to acquire the water temperature.
I explayin how to do, looking to the Yamaha R6 electrical circuit manual, the water temperasture sensor (#23 in the picture) is directly connected to the ECU:

Therefore is quite simple to connect it: just take a cable and solder it on the ECU connector G/W (Green/White- mainly is a green cable with a little white stripe) cable, bring it to the XE164 KeyChain and compute the temperature as:

uiTmp = (unsigned int) ( ((float) ( uiTemperature >> 4) ) * (-1.32) + 127.42 )
/*
uiTemperature is the 12-bit ADC converted values, before temperature calculation I reduce the precision to have stable temperature visualization (I do not need so high precision)
*/

I've used such equation since I have desumed from the Yamaha manual the following NTC curve (it declares that the NTC has 6.37KOhm at 0°C and 0.35kOhm at 80°C):
Temperature Vs. NTC resistance

The same could be plotted as Temperature Vs. ADC Voltage
Temperature Vs. ADC Voltage

Looking to the same, but plotting Temperature Vs. ADC value in the range 60°C .. 110°C (the most important temperature range), we get:
Temperature Vs. ADC value
and this is what I measured:

After a little rearrangement, I fit it better:

Now I calculate the SLOPE and the INTERCEPT (I assume a linear equation to have a simple calculation):
SLOPE = -1.32
INTERCEPT = 127.42